This invention relates generally to ink jet printers and, more particularly, to an integrated circuit for the printhead of the ink jet printer, wherein the integrated circuit contains a resistor array and an identification circuit.
Referring now to FIG. 1, shown therein is a print cartridge 10 for an ink jet printer. The print cartridge 10 contains ink reservoirs and the integrated circuit (neither are shown in FIG. 1), a printhead 12, a printhead opening or "orifice plate" 11 having a plurality of nozzles for passing a plurality of ink jets, and a flexible "tab" circuit 20 that allows for electrical connection of the printhead 12 to the ink jet printer in which the cartridge 10 is installed. Thin film resistors in the integrated circuit resistor array selectively boil ink in the ink reservoir to produce a predetermined ink jet pattern. The placement of the integrated circuit resistor array is best seen in FIG. 3 and is described below.
Referring now to FIG. 2, the printhead 12 and tab circuit 20 are shown in greater detail. The tab circuit 20 is a lead frame type of flexible ("flex") circuit that generally comprises a flexible planar dielectric substrate or film having a metalization pattern formed on one surface thereof by, for example, sputter deposition and photolithographic etching. The back side of the flex tab circuit 20 that contains the metalization pattern is bonded to the integrated circuit in the print cartridge 10 using integrated circuit fabrication techniques. The front side of the flex tab circuit 20 contains ground pads 25 and interconnect pads 17 for electrical connection to the ink jet printer. Also shown in FIG. 2 is further detail of the orifice plate 11, which is surrounded by insulating adhesive beads 35 for encapsulating the interconnect conductive traces to the integrated circuit in the printhead 12. The back side of the flex tab circuit 20 is shown in greater detail in FIG. 3. The metalization pattern on the back side of circuit 20 includes conductive traces 13 separated and insulated by predetermined spaces 21. The conductive traces 13 connect the integrated circuit (shown generally at 15) to the back side of the interconnect pads 17.
The printhead 12 of the print cartridge 10 is shown in greater detail in FIG. 4 along perspective lines 4--4 of FIG. 2. The simplified cross-sectional of view of FIG. 4 reveals the placement of the integrated circuit 26, which includes the thin film resistor array, in the ink reservoir 28. The ink immediately above the integrated circuit 26 is boiled and forced through nozzles 27, forming a pattern of ink jets.
In an ink jet printer as described above and shown in FIGS. 1-4, it is desirable to have several characteristics of each print cartridge 10 easily identifiable by a controller in the printer. Ideally the data should be supplied directly by the print cartridge 10. The "identification data" provides feedback to the controller that adjusts the operation of the printer and ensures correct operation. The identified printer characteristics include, but are not limited to, ink color, architecture revision, resolution, number of nozzles 27 in the orifice plate 11, spacing between the nozzles 27, among others. In addition to the above characteristics of the print cartridge 10, it may be further desirable to characterize each print cartridge 10 during manufacturing and to supply this information to the printer. In this manner, it would be possible compensate for variations in energy supplied by the resistor array in the integrated circuit 26, ink drop volume, ink drop velocity, missing nozzles, and various other manufacturing tolerances or defects such as orifice plate 11 misalignment or non-planarity and angled orifice holes 27.
While the identification information supplied by the print cartridge 10 to the printer as described above is highly desirable, it is not desirable to add further interconnect pins 17 to the flex tab circuit 20 to carry such information. The requirements that the interconnection between the print cartridge 10 and the printer be reliable, that the print cartridge be made as small as possible, and the mechanical tolerances of the interconnect pads 17 mandate that the number of interconnect pads 17 be kept to a minimum.
Accordingly, what is desired is a method and apparatus for generating identification data directly in the print cartridge 10 to be supplied to a controller in the ink jet printer, while minimizing or even eliminating the number of additional interconnect pads 17 required to carry the identification data.